Aqueous dispersions of phenyl-betanaphthylamine



Patented Apr. 19, 1949 AQUEOUS DISPE-RSIQN S fiFiPHENYL-LBETANAPHTHYLAMINE Bernard M. 'Sturgis, Pitman, N. J., assignor to E. I. duPont de Nemours & Company, Wilmington, De1., a corporation of DelawareNo Drawing. Application January .25, 1946., Serial No. 643,484

*4 Claims. (Cl. 252- 311) This invention relates to the preparation ofstable aqueous dispersions of 'phenyl-betanaphthy-lamine, which areparticularly useful as anti- :oxidants in the elastomer field.

The secondary aromatic amines, such as 'phenyl-beta-naphthylamine, whichare ployed as anti-oxidants in the rubber and synthetic rubberindustries, when employed with rubber latices or other aqueousdispersions of synthetic elastomers are preferably incorporated in suchlatices as aqueous dispersions. aqueous dispersions of the amines areprepared with'the aid of dispersing agents by the methods "usuallyemployed for dispersing solids in liquids. @rdinarily, the aromaticamine anti-oxidant dispersion is made up, as it is used, inconcentrations of from 10% to 60%, and such dispersions are added to thelatex in carefully measured amounts prior to the coagulation and dryingof the elastomer. The aqueous dispersions of the secondary aromaticamines prepared by the methods heretofore employed are often not stable,and, on standing even for short periods oftim'e, the amine settles outquite rapidly. Such sedimentation makes the handling, measuring Theseand proper addition of the amine to the latex d ifiicu'lt. When suchsettling out of the dispersion occurs, it tends to plug pumps, valvesand lines. It will also be obvious that, in such case, the amount ofanti-oxidant actually added to the latex cannot be accuratelydetermined, and therefore it is important, for smooth operation of theprocess, that stable dispersions of the anti-oxidants be 'used.

It is difiicult to make stable aqueous dispersions methods of dispersingsolids in water, such as by grinding in a ball mill or even with the useof such efiicient apparatus as the colloid'mill. While most of thecommercial wetting or dispersing agents give improved results when addedto such suspensions, even the most efficient dis- :persin'g agents oftenfail to produce dispersions 0f iphenylbeta-naphthylamine which will not*settle out after short periods of standing. The addition of largeramounts of "the dispersing agent does not produce the desired stability.

.' It is therefore an object of this invention to provide a method ofproducing aqueous dispersions of phenyl-beta-naphthylamine with improvedstability with regard to settling. A further object of the invention isto produce the phenyl-beta-naphthylamine in a form such that it can bereadily dispersed in water by the usual methods, but which will givesuspensions that of phenyl-beta-naphthylamine by the usual are much morestable with regard to settling than are ordinarily obtained. A furtherobject of the invention is to produce aqueous dispersions ofphenyl-beta-naphthylamine in higher concentrations than has normallybeen possible and which will remain dispersed when .diluted in water for.a .sufiicient time to permit suitable processing of the rubber laticeswith which they are incorporated.

. I have found that greatly improved aqueous dispersions ofphenyll-betaenaphthylamine -.can be produced by adding to the amine asmall amount of a straightchain primary aliphatic mercaptan containingfrom .8 to 14 carbon atoms, in which group the one containing 12 carbonatoms is preferred. The mercaptan is preferably added to theamine duringthe manufacture or flaking process, as more particularly illustrated inthe following example, although it may be added during the'preparation.of the dispersion by adding it to the aqueous suspension and subjectingthe mass :to a milling or colloidal grinding operation. It appears thatthe mercaptan must be incorporated in such a manner that it has intimatecontact with the dispersed particles of the phenyl-beta-naphthylamine,for, by merely adding the mercaptan to the already prepared dispersionwithout again subjecting the .mass to conditions which would ordinarilydisperse the solid in a liquid, the same results are not obtained aswhen the mercaptan is added to the amine during or prior to thedispersion operation. These mercaptans are efiective as dispersing aidsin amounts ranging from 0.1% to 10%,, although practical limits of useare from 0.1% to 3%, based on the weight of the,phenyl-beta-naphthylamine. Mixtures of mercaptans of this type appearto be as efiective as the pure mercaptans by themselves.

This invention is applicable particularly in improving the dispersionstability of phenylbeta-naphthylamine used as an anti-oxidant for rubberor other .elastomers.

As pointed out above, the mercaptan may be added to thephenyl-beta-naphthylamine during the manufacture of the amine, or it canbe intimately incorporated with the amine by a mix- .ing 'or millingoperation so that the amine is put in a form that can be readilydispersed in water by the user by the methods generally employed inpreparing the amine dispersion. Alternatively, the mercaptan can beadded to the water, amine and dispersing agent at the start of thedispersion process, or during the dispersion process. These mercaptanswill function in any of the common dispersion processes wherein thephenyl-beta-naphthylamine is dispersed in water with a dispersing agent.

The straight chain primary aliphatic mercaptans in themselves do notappear to have properties of dispersing agents, and they function as adispersing aid where the phenyl-beta-naphthylamine is dispersed in waterby means of the usual dispersing agents. The preferred dispersing agentis the sodium salts of the reaction product mine. These dispersions,being more stable, can be used over much longer periods of time withoutsettling out. By the addition of the straight chain mercaptans, of thetype described as a dispersing aid, greatly improved dispersions areobtained, usually being much smaller in particle size, having lowerviscosity for a given concentration, and having less tendency to foam.By

" the addition of these dispersing aids, much of naphthalene,formaldehyde, and sulfuric acid, I

as more particularly disclosed in U. S. Patent 1,-

other dispersing agents, such as the sodium salts of sulfated laurol orother alcohols, or mixtures of the same, purified sulfolignins, and thesodium salts of aliphatic sulfonates of petroleum hydrocarbons orsimilar dispersing agents, may be employed in place of the sodium saltsof the naphthalene-formaldehyde-sulfuric acid condensation product.

The following example is given to illustrate the invention, in whichparts used are by weight.

Example One thousand (1000) parts of phenyl-betanaphthylamine and 10parts of n-dodecyl mercaptan were melting and flaked in a conventionaldrum type fiaker, holding the melted material in the fiaker pan at 140to 150 C. and the surface of the drum at 90C. The flaked material water,shaken vigorously and allowed to stand' for 20 minutes. No sedimentcould be seen at the bottom of the cylinder at the end of this time andno sediment remained behind when the liquid was carefully poured out. Onthe other hand, when no mercaptan was incorporated in the amine, theresulting dispersion gave 10.5 cc. of sediment in the test and thisremained in the cylinder after pouring off the liquid.

Any of the other straight chain primary aliphatic mercaptans containingfrom 8 to 14 carbon atoms, such as the octyl, nonyl, decyl, tetradecylmercaptans, may be substituted for the n-dodecyl mercaptan in the aboveexample to give stable dispersions of the phenyl-beta-naphthylaminesimilar to that obtained with the ndodecyl mercaptan.

When the number of carbon atoms is less than 8 or more than 14, themercaptan has little or no favorable effect upon the stability of theamine dispersions. Thus, hexyl mercaptan, with 6 carbon atoms, gave 5cc, of sediment both before and 'after decantation in the test,pentadecyl mercaptan (15 carbon atoms) gave 6 cc., and cetyl mercaptan(16 carbon atoms) gave 10 cc.

The use of the primary straight chain aliphatic mercaptans of from 8 to14 carbon atoms enables the production of greatly improved aqueousdispersions of the phenyl-beta-naphthylasmaller amounts of thedispersing agent may be employed.

The dispersions formed according to the present invention may be addedto any aqueous dispersion of oxidizable organic materials requiringstabilization by means of secondary aromatic amines.

I claim:

1. In the process for preparing aqueous dispersions ofphenyl-beta-naphthylamine wherein the phenyl-beta-naphthylamine isdispersed in water by means of a water soluble dispersing agent, thesteps which comprise incorporating in such aqueous dispersion, beforethe dispersion process is completed, from 0.1% to 10%, based on theweight of the amine, of a straight chain primary aliphatic mercaptancontaining from 8 to 14 carbon atoms, and completing the dispersionprocess by a colloidal mixing operation,

2. An aqueous dispersion of phenyl-beta-naphthylamine which has beenprepared by a colloidal mixing operation and which in addition to thewater and phenyl-beta-naphthylamine consists of a water solubledispersing agent and as a dispersion aid from 0.1% to 10%, based on theweight of the amine, of n-dodecyl mercaptan.

3. A phenyl-beta-naphthylamine composition which is readily dispersiblein Water by a colloidal mixing operation with the aid of a water solubledispersing agent to give a dispersion which has improved stability withregard to settling, consisting of said amine having intimatelyincorporated therewith from 0.1% to 10%, based on the weight of theamine, of a straight chain primary aliphatic mercaptan containing from 8to 14 carbon atoms.

4. A phenyl-beta-naphthylamine composition which is readily dispersiblein Water by a colloidal mixing operation with the aid of a water solubledispersing agent to give a dispersion which has improved stability withregard to settling, consisting of said amine having intimatelyincorporated therewith from 0.1% to 10%, based on the weight of theamine, of n-dodecyl mercaptan.

BERNARD M. STURGIS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,355,985 Lilienfeld Oct. 19,1920 1,977,211 Schur Nov. 30, 1937 2,100,714 Hiers Nov. 30, 19372,227,517 Starkweather Jan. 7, 1941 2,234,204 Starkweather Mar. 11, 19412,281,613 Wollthan May 5, 1942

